What is customizing-shelley?

Instructions for changing Shelley, the coding agent, itself, including its code, interface, tools, or behavior. It also covers updating a customized Shelley build.

Modifying Shelley’s implementation or UI, changing its tools or behavior, and rebasing or upgrading a customized build.

It explains how to handle changes that cannot be made through Shelley’s normal hooks and how to keep a customized version up to date.

customizing-shelley — Skill for Claude Code and Codex by boldsoftware

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add boldsoftware/shelley --skill customizing-shelley

Clone the repo

git clone --depth 1 https://github.com/boldsoftware/shelley

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/boldsoftware/shelley/customizing-shelley/github.svg)](https://agentmods.dev/skills/boldsoftware/shelley/customizing-shelley)

Your own site

<a href="https://agentmods.dev/skills/boldsoftware/shelley/customizing-shelley"><img src="https://agentmods.dev/badge/skills/boldsoftware/shelley/customizing-shelley/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/boldsoftware/shelley/customizing-shelley"><img src="https://agentmods.dev/badge/skills/boldsoftware/shelley/customizing-shelley.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 42 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,186 The whole file, excluding the scripts and references it only reads on demand.

Security scan B 2 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin unknown No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00042	$0.01186
Opus 5.5	$0.00017	$0.00474
Sonnet 5.5	$0.00008	$0.00237
Haiku 4.5	$0.00004	$0.00119

Measured 13d ago against content hash dac46252a827, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade B, and why

customizing-shelley scanned grade B with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 13d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Asks for rootmediumPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

sudo cp -p "$DEST" "$DEST.new"

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -s "$SHELLEY_URL/version-check" | jq -r .executable_path

skills/builtin/customizing-shelley/SKILL.md · 89 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

13d ago Changed dac46252a827
15d ago Changed · -1 lines aa98c4afd6af
24d ago Changed 201ef24ef399
2mo ago First seen · 90 lines · 42 tokens per session scan B 355c671465e2

Subscribe to this mod's changes

customizing-shelley is a skill published in the GitHub repository boldsoftware/shelley (716 stars, last pushed yesterday), with no licence file. It adds 42 tokens to every session and 1,186 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it B with 2 findings (asks for root, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Building agents

customizing-shelley next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
customizing-shelleyboldsoftware/shelley	Skill	716	yesterday	none	B	42	Claude Code, Codex
imagegenopenai/codex	Skill	133k	yesterday	Apache-2.0	A	113	Codex
playwright-climicrosoft/playwright	Skill	99k	yesterday	Apache-2.0	A	19	Claude Code
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	4d ago	MIT	A	200	Claude Code, Codex
systematic-debuggingobra/superpowers	Skill	313k	3d ago	MIT	A	21	Claude Code
next-cache-components-adoptionvercel/next.js	Skill	143k	today	MIT	A	95	Claude Code
next-partial-prefetching-adoptionvercel/next.js	Skill	143k	today	MIT	A	103	Claude Code